README: fix path to requirements.txt, re-order sections giving prominence to installation & usage
Update README.md
installing from requirements.txt requires sudo on Mac

Also, since we ```cd slyd``` already, we don't need slyd/requirements.txt
Merge pull request #44 from ray-/master

installing from requirements.txt requires sudo on Mac
Update README.md
- Fixes issue #53

Support '-' and '~' in spider names.
fix BaseSpider usages
Merge pull request #58 from kmike/basespider-deprecation

fix BaseSpider usages
- Modifies the annotation workflow.

Implements workflow suggestions discussed with Oleg.
- portia can now be run using vagrant.
Updates the Vagrant file to version 2 format.
sudo is not needed in the provisioning script.
Ignore files created when running vagrant.
- Tiny style update
Added instructions to run portia with vagrant.
DOC: add prerequisites section
Merge pull request #69 from tpeng/improve-docs

DOC: add prerequisites section
disable the http cache by default and allow override setting in local_settings close #68
allow pass extra settings for portiacrawl
fix Portia for Scrapy 0.24